Flexible expandable conveyors which use lazy tong support frames or structures have been widely used for many years. Lazy tongs are structures formed of a set of generally parallel bars, each of which is pivotally connected at its end points and midpoint to other bars in another, transversely oriented, set of parallel bars so that the structure may be extended and retracted with scissors-like action.
Lazy tong conveyors are particularly useful to move packages and other items from one point to other points in a plant or warehouse, and in loading or unloading trucks, airplanes, or containers. They may be flexed and extended or retracted with minimum effort to lead to the desired location, vehicle, or container.
First generation lazy tong conveyors, such as the ones disclosed in U.S. Pat. No. 3,276,558 issued Oct. 4, 1966 to Guske, et al. and U.S. Pat. No. 4,266,650 issued May 12, 1981 to Patel, et. al., which are incorporated herein by reference, provided flexibility at the expense of durability. The axles connecting the lazy tong structures and carrying the skate-wheels are easily bent as packages or other items are thrown onto the conveyor and create great impacts and high loads. Such items frequently impact on only one skate-wheel and thus easily deform its supporting axle. Packages or items hitting a skate-wheel from the skate-wheel's side subject the skate wheel and axle to additional bending moments and cause further deformation.
Second generation conveyors, such as those disclosed in U.S. Pat. No. 4,852,712 issued Aug. 1, 1989 to Best, which is incorporated herein by reference, provided additional durability through the use of brace systems or other supports. The braces, which are rigidly connected to the bars of the lazy tong structures and to the axles using clips intermediate skate wheels, lend additional support to the skate-wheels and axles. Second generation conveyors are more complex than first generation conveyors. The brace systems of second generation conveyors are problematic in that they require many different parts, are expensive to build, and take longer to construct than conveyors not using brace systems. Moreover, if an axle or a component of the brace system fails, disassembling and rebuilding the axle and brace system's many parts would require a large amount of time.
Some conventional conveyors utilize axle supports to improve load bearing capability of the roller wheels connected to a combination of an axle with the axle support. In at least one conveyor, the axle support is maintained in a vertical orientation to optimize load bearing capability of the roller wheels. That conveyor has a lower span that traverses the axle support at a lower yoke portion of the axle support to maintain vertical orientation of the axle support. In some instances, the vertical orientation of the axle support cannot be maintained by the lower span, and the load bearing capability of the conveyor is reduced.